@@ -231,6 +231,27 @@ __efi64_mb2_start:
/* VGA is not available on EFI platforms. */
movl $0,vga_text_buffer(%rip)
+ /*
+ * Align the stack as UEFI spec requires. Keep it aligned
+ * before efi_multiboot2() call by pushing/popping even
+ * numbers of items on it.
+ */
+ and $~15, %rsp
+
+ /*
+ * Initialize BSS (no nasty surprises!).
+ * It must be done earlier than in BIOS case
+ * because efi_multiboot2() touches it.
+ */
+ mov %eax, %edx
+ lea __bss_start(%rip), %edi
+ lea __bss_end(%rip), %ecx
+ sub %edi, %ecx
+ shr $3, %ecx
+ xor %eax, %eax
+ rep stosq
+ mov %edx, %eax
+
/* Check for Multiboot2 bootloader. */
cmp $MULTIBOOT2_BOOTLOADER_MAGIC,%eax
je .Lefi_multiboot2_proto
@@ -321,34 +342,12 @@ __efi64_mb2_start:
lea .Lmb2_no_ih(%rip),%r15
jz x86_32_switch
- /*
- * Align the stack as UEFI spec requires. Keep it aligned
- * before efi_multiboot2() call by pushing/popping even
- * numbers of items on it.
- */
- and $~15,%rsp
-
/* Save Multiboot2 magic on the stack. */
push %rax
/* Save EFI ImageHandle on the stack. */
push %rdi
- /*
- * Initialize BSS (no nasty surprises!).
- * It must be done earlier than in BIOS case
- * because efi_multiboot2() touches it.
- */
- lea __bss_start(%rip),%edi
- lea __bss_end(%rip),%ecx
- sub %edi,%ecx
- shr $3,%ecx
- xor %eax,%eax
- rep stosq
-
- /* Keep the stack aligned. Do not pop a single item off it. */
- mov (%rsp),%rdi
-
/*
* efi_multiboot2() is called according to System V AMD64 ABI:
* - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
@@ -434,6 +433,8 @@ __pvh_start:
/* Set up stack. */
lea STACK_SIZE - CPUINFO_sizeof + sym_esi(cpu0_stack), %esp
+ call .Linitialise_bss
+
mov %ebx, sym_esi(pvh_start_info_pa)
/* Force xen console. Will revert to user choice in init code. */
@@ -459,6 +460,25 @@ __pvh_start:
#endif /* CONFIG_PVH_GUEST */
+.Linitialise_bss:
+ /*
+ * Initialise the BSS.
+ *
+ * !!! WARNING - also zeroes the current stack !!!
+ */
+ pop %ebp
+ mov %eax, %edx
+
+ lea sym_esi(__bss_start), %edi
+ lea sym_esi(__bss_end), %ecx
+ sub %edi, %ecx
+ xor %eax, %eax
+ shr $2, %ecx
+ rep stosl
+
+ mov %edx, %eax
+ jmp *%ebp
+
__start:
cld
cli
@@ -489,6 +509,8 @@ __start:
/* Set up stack. */
lea STACK_SIZE - CPUINFO_sizeof + sym_esi(cpu0_stack), %esp
+ call .Linitialise_bss
+
/* Bootloaders may set multiboot{1,2}.mem_lower to a nonzero value. */
xor %edx,%edx
@@ -645,26 +667,6 @@ trampoline_setup:
* reserved for trampoline code and data.
*/
- /*
- * Do not zero BSS on EFI platform here.
- * It was initialized earlier.
- */
- cmpb $0, sym_esi(efi_platform)
- jnz 1f
-
- /*
- * Initialise the BSS.
- *
- * !!! WARNING - also zeroes the current stack !!!
- */
- lea sym_esi(__bss_start), %edi
- lea sym_esi(__bss_end), %ecx
- sub %edi,%ecx
- xor %eax,%eax
- shr $2,%ecx
- rep stosl
-
-1:
/* Interrogate CPU extended features via CPUID. */
mov $1, %eax
cpuid
Allows to call C code earlier. In order to safely call C code we need to setup stack, selectors and BSS. Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com> --- Changes since v1: - improve commit message; - improve some comments; - fix some code style (spacing); - set trampoline_phys as 32 bit value; - use PAGE_SIZE mnemonic instead of 0x1000; - use local label. --- xen/arch/x86/boot/head.S | 86 ++++++++++++++++++++-------------------- 1 file changed, 44 insertions(+), 42 deletions(-)